1) Field of the Invention
The present invention relates to an apparatus for recording and/or reproducing optical information on/from a card-like information recording medium, such as an optical card, and particularly relates to an apparatus in which an optical head provided in the apparatus and the recording medium are arranged to be relatively moved with respect to each other in a longitudinal direction of the recording medium and a direction perpendicular thereto. According to the present invention, the relative movement of the optical head and the recording medium is controlled so as not to damage the optical card and the recording medium.
2) Description of the Related Art
On an optical card, it is impossible to rewrite optical information, once information has already been written on. However, the optical card has a great memory capacity, i.e. about several thousand times to ten thousand times as large as that of a magnet card. The optical card has its memory capacity of about from one to two megabytes, so that a great number of applications such as a bankbook, a pocket map and a prepaid card for shopping can be considered on the optical card.
Many constructions of optical cards have been suggested; and one of the constructions of the optical card, which has been suggested by the applicant in Japanese Preliminarily Laid-open Publication No. 63-37836, is shown in FIG. 1. On the optical card 11, there is provided an optical information recording portion 12, which comprises a plurality of tracks 13 extending in a longitudinal direction (track direction) of the optical card 11, being parallel to each other. On both sides of the optical information recording portion 12, there are arranged ID portions 14A and 14B, respectively, and an information recording area 15 therebetween. In each ID portion 14A and 14B, address information corresponding to each track 13 is recorded.
In an apparatus by which optical information is recorded and/or reproduced on/from such optical card by moving the optical head and the optical card in a relative and reciprocal manner, the optical card is generally held in a container, which is a so-called shuttle; the shuttle containing the optical card therein is arranged to be relatively moved with respect to the optical head in the track direction; and the optical head is arranged to be relatively moved with respect to the optical card in a direction perpendicular to the track direction (tracking direction). FIG. 2 is a plan view showing the positional relation between the optical head 31 and the shuttle 21 containing the optical card 11 in the apparatus. The arrow A represents the track direction along which the shuttle 21 is relatively moved with respect to the optical head 31, and the arrow B represents the tracking direction, perpendicular to the track direction, along which the optical head 31 is relatively moved with respect to the optical card 21.
In such apparatus for recording/reproducing optical information on/from an optical card, the shuttle is generally driven with the aid of a driving motor, such as a linear motor. When some accident happens in a driving system for moving the shuttle, there is a possibility that the shuttle is moved over its movable limitation. Therefore, when some accident happens in the driving system, an electric supply for the driving motor should be stopped in order to prevent breakage of the linear motor.
In order to solve such problem, in Japanese Utility Model Preliminarily Publication No. 63-81366, is disclosed an apparatus having stoppers on both end portions of a shaft for supporting the optical head. There are provided two electric conductors on the stoppers, respectively, and there are also arranged plastic members having electric conductivity on both ends of the optical head in its moving direction; and the contact of the optical head and the stoppers are detected by a detector, which is arranged to detect the fact that the electric conductors electrically shorten when the optical head makes contact against the stoppers. Further, in Japanese Utility Model Preliminarily Publication No. 63-99367, is disclosed an apparatus having magnetoelectric elements on both end portions of a movable distance of an optical head and plastic magnet members on both end portions of the optical head. Therefore, the fact that the movable body arrived to the end portions of the movable distance thereof is detected with the aid of the magnetoelectric elements. Furthermore, in Japanese Utility Model Preliminary Publication No. 63-109580 is disclosed an apparatus having buffer members having an electric conductivity on both end portions of a movable range of coils of an optical head, and the buffer members are connected to an electric circuit by which an electric supply for the coils is stopped when the optical head has moved over the movable range.
As stated above, in the conventional apparatuses, there are provided limit switches at both end portions of movable range of the movable body, such as optical head, magnetic head and coils provided therein, so as to detect that the movable body has moved to the end portions of the range; and then the electric current supply to the driving motors for driving the movable body is interrupted. However, in the conventional apparatuses, there is a drawback that the construction of the apparatus becomes complex and the cost for manufacturing would increase because the limit switches are arranged only for the purpose of detecting that the movable body has moved to the end portions of the range.
FIG. 3 is a side view showing the positional relation between the optical head 31 and the shuttle 21 containing the optical card 11 therein. The shuttle 21 comprises an auxiliary plate 21a and a press plate 21b which serve to hold the optical card 11 therebetween at a desired position without deviation, a spring 21c for energizing the press plate 21b in an upper direction, and a base plate 21d. The optical card 11 is inserted between the auxiliary plate 21a and the press plate 21b; and the spring 21c is arranged between the press plate 21b and the base plate 21d. The press plate 21b is energized with respect to the auxiliary plate 21a by means of the spring 21c, so that the optical card 11 is contained in the shuttle 21 in a stable manner. The shuttle 21 is reciprocally moved in the track direction by a driving motor (not shown in FIG. 3).
In such conventional apparatus, there is a possibility that when a driving circuit for driving the optical head 31 is damaged, for example, when the optical head 3 is driven over the movable range thereof. As clear from FIG. 3, an objective lens 31d of the optical head 31 is generally positioned in a level lower than the level of the upper surface of the auxiliary plate 21a, due to a working distance of the objective lens 31d. Therefore, when the optical head 31 has been moved over the movable range thereof, the objective lens 31d would collide against the auxiliary plate 21a; and in the worst case the objective lens 31d would be broken so that optical information could not be recorded/reproduced on/from the optical card 11 any more.
In the optical card 11 shown in FIG. 1, there are provided ID portions 14A and 14B on both sides of the optical card 11 in its longitudinal direction; therefore address information of each track recorded thereon can be read out when the optical card 11 is moved with respect to the optical head not only from right to left but also from left to right. That is to say, when optical information is recorded/reproduced by moving the optical card 11 from the left side to the right side in the track direction, the desired track is recognized with the aid of track address information recorded on the left side ID portion 14A; and when optical information is recorded/reproduced by moving the optical card 11 from the right side to the left side the desired track is recognized with the aid of track address information of the right side ID portion 14B. It should be noted that the ID portions 14A and 14B are arranged inside by a given distance from both ends of the optical card 11. The margins outside the ID portions are arranged in order to proof the influence of defect or dirt formed on the edge portions of the optical card 11. The margins are further utilized as an acceleration and deceleration area. That is to say, the moving speed of the optical card 11 is accelerated at one of these areas, at a constant speed between ID portions 14A and 14B and then decelerated at another ID portion.
In the apparatus, in which the optical card 11 is used as an information recording medium, information is recorded on the optical card 11 such that the optical card 11 is reciprocally moved in the track direction between the ID portion 14A and 14B at a constant speed; a clock signal is produced in a clock generating circuit, which is arranged to be independent from the movement of the optical card 11; a light beam emitted form a light source in the optical head 31, which is modulated being synchronized with the clock signal, is made incident upon the optical card 11. While, information is reproduced from the optical card 11 such that, clock signal is produced in accordance with an information reproducing signal obtained by detecting a reflection light beam reflected by the optical card 11; then the information reproducing signal is demodulated being synchronized with the clock signal obtained thereby.
In such an apparatus, it is desired that a variation of the relative moving speed of the optical card 11 and the optical head 31 between the ID portions 14A and 14B be almost zero. However, in order to make such variation zero, it is necessary to control the systems in the apparatus in a very complex manner; and then the cost for manufacturing the apparatus would be increased. Additionally, in the apparatus, the optical card and the optical head should be relatively moved between the ID portions 14A and 14B at a constant speed in order to record/reproduce optical information on/from the optical card in a good manner. Therefore, in the apparatus for the optical card, it is necessary to repeat the following steps that: the optical card 11 and the optical head 31 are started to be moved, the moving speed thereof is increased, decreased, and then stopped. However, in case the optical card is used as a recording medium, it is more difficult to control the relative moving speed of the optical head and the optical card in an exact manner in comparison with the optical disc, in which the optical disc is rotated in a given direction.
When information is reproduced from the optical card 11, the clock signal is produced in accordance with the information reproducing signal, which is obtained from the reflection light beam reflected by the data portion 15 of the optical card 11, and the information reproducing signal is demodulated being synchronized with the thus obtained clock signal. Thus, in case the variation of the relative moving speed of the optical head 31 and the optical card 11 is limited to a range, in which the clock signal can be produced, information could be reproduced without difficulty. However, when information is recorded on the optical card 11, the frequency of the clock signal for recording is not varied in accordance with the variation of the relative movement of the optical head 31 and the optical card 11. Therefore, the variation of the relative movement would make an influence to the information recording effect. If the variation of the relative movement when information is recorded is so large, that the variation of the relative movement when information is reproduced would substantially become large because the variation would be superimposed with the variation of the relative movement caused when information is recorded. Therefore, the information reproducing function of the apparatus would be decreased.
In case the optical card 11 having two ID portions 14A and 14B at both sides thereof as shown in FIG. 1 is used as an information recording medium, when the relative moving speed of the optical card 11 and the optical head 31 under the information recording manner is faster than the desired speed, a margin for the variation of the readable relative moving speed of the optical card and the optical head would be decreased. And in the worst case, ID portions 14A and 14B would be damaged due to the variation.
Even in case an optical card having one ID portion at one side thereof is used as an information recording medium, a margin for the variation of the readable relative moving speed of the optical card and the optical head would be decreased. And in the worst case, ID portions 14A and 14B would be also damaged.
On the other hand, the relative moving speed between the optical card 14 and the optical head 31 is slower than the desired speed, in case the optical card having two ID portions at both sides thereof is used as an information recording medium, the margin for the variation of the readable relative moving speed would be decreased; and in case the optical card having only one ID portion is used, not only the margin for the variation of the readable relative moving speed would be decreased but also the relative moving speed would not be increased upto the desired speed although the optical head is positioned at the information recording area of the optical card, so that the reproduction signal could not be reproduced.